One of the most common issues people discuss when they're talking about energetic healing and prayer is permission: you're not supposed to send healing energy to anyone without their permission. But I don't think it's as simple an issue as it sounds.
I've been an herbalist for nearly 30 years, a Reiki master for 15, a witch/Pagan priestess for 30+, and I used to have a naturopathy consultation practice, so I've dealt with all kinds of healing in a variety of settings. And I can tell you, there's far more to it than just asking someone for permission.
First of all, the human psyche complicates things. You can ask someone for permission and hear them say yes, then watch as they reject every single bit of healing energy you send their way. This is because they can't admit to themselves that they're not ready to receive healing yet. It happens a lot more than you might think, and I've even caught myself doing it once or twice.
The flip side of that situation is that a person can say no when you ask permission, for a variety of reasons, but actually desire healing on a deeper level. Perhaps, on the surface, they feel they don't deserve to be helped, as if they aren't worthy or they deserve to suffer. But somewhere inside, they know that isn't true, and they want the healing.
So here's how I handle it. First of all, I never physically touch anyone without explicit permission, regardless of what I think their underlying desires or motives might be. That's a hard boundary that everyone should abide by, IMO.
But for energetic healing and prayer (lighting a candle, sending good vibes, sending Reiki long distance, etc.) I have a specific "disclaimer" I use: I offer the energy for whatever they want and need it for, with the caveat that they're free to accept or reject any or all of it as they like, preferably under advisement from their spirit allies, higher self, or however they experience that sort of thing. That way, I'm not forcing the healing on anyone, simply offering it if they want it. I guess you could call it energetic consent.
Consent is important on a lot of levels, and I think it's imperative we include it. As for the fundamentalist Christians who like pray for me and push me toward what they think is the One True and Right Way (TM)? That crap bounces off and goes right down the drain.